The invention relates generally to power systems and more specifically to a method and system for a dual mode rectifier.
Many devices, such as power supply systems, operate on power drawn from generators. The generator, in turn, draws power from systems such as wind turbines, gas or diesel-driven engines, turbines, or any other suitable drive system. The output of the generator is typically a variable frequency output power.
Typically, rectifiers are used to convert the variable frequency output power to a fixed frequency output power. Converters are then used to convert the fixed frequency output power to a desired frequency output power, which is then provided to various loads such as grid. In other applications, such as motors, power converters are designed to draw power from a grid and provide the power to the motor.
Rectification can be of two types namely passive rectification or active rectification. Passive rectification is performed using diode bridges. Passive rectifiers deliver power from an active source with high efficiency but do not provide control over the power drawn from the source. In addition, passive rectification introduces harmonics in the ac side current, which cause undesirable torque harmonics when the active source is a generator or unacceptable distortions when the active source is the power grid.
Active rectifiers, on the other hand, can be controlled as they are implemented using switches. One problem with active rectifiers is the associated cost. In addition, active rectifiers operate at a lower efficiency due to losses caused by the switching action of the semiconductor devices.
In many applications, low speed high torque generators are required. Such generators are larger in size than generators running at higher speeds. The size of the generator also increases if it is operated at lower power factor. The large size of the generator in turn increases the cost substantially.
Therefore, what is desired is a rectifier system that operates at a high power factor and high efficiency while minimizing the cost and the size of the rectifier system.